68 THE CANADIAN NATURALIST. [Vol. X. 



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streams come from northward of the escarpment, and belong to 

 a system of drainage different from those streams which flow 

 down through the drift of the Duudas valley and are of much 

 greater length. At the foot of* Spencer Falls, the waters strike 

 the upper portion of the Clinton shaly beds. The Falls now 

 are two feet deeper than twenty years ago. Yet the stream is 

 small, and makes a pond below in the soft shales. But this 

 difference in height does not represent the rute of wearing or 

 recession of the precipice. That the stream is much smaller 

 than formerly is plainly to be seen, for at present it has cut a 

 narrow channel, from ten to fifteen yards in width, above the 

 falls, and from four to six feet deep on one side of the more 

 ancient valley, which is about 50 yards wide and 30 feet deep, 

 excavated in the Niagara dolomites. 



The surfaces of the escarpment in both sides of Glens Spencer 

 and Webster present a peculiar aspect. That on the north-eastern 

 side has a maximum heio-ht of 520 feet above the lake. On the 

 same side, a section made longitudinally shows several broad 

 shallow glens nearly a hundred feet deep crossing it and entering 

 Olen Spencer. The surface of the rocks is glaciated, but not 

 parallel with the direction of the channels. On the south-western 

 side of the same canon, we find that a portion of the thin beds 

 of Upper Niagara limestone have been removed. This absence 

 is not general, for it soon regains its average height of about 500 

 feet. 



The Grand River Valley. The Grand River of Ontario rises 

 in the County of Grey, not more than twenty-five miles from 

 Georgian Bay. Thence it flows southward, and at Flora the river 

 assumes a conspicuous feature. Here it cuts through the Guelph 

 dolomites to a depth of about 80 feet and forms a canon about 

 100 feet in width with vertical walls. At this place it is joined 

 by a rivulet from the west, which has formed a tributary canon 

 similar to that of the Grand River itself 



The country in this region is so flat that it appears as a level 

 plane. Farther southward the river winds over a broader bed, 

 and at Gait the present river valley occupies a portion of abroad 

 depression in a country indicating a former and much more ex- 

 tensive valley. In fact the old river valley existed inPreglacial 

 times, for the present stream has re-excavated only a part of its 

 old bed at Gait, leaving on the flanks of one of its banks (both 

 of which are composed of Guelph dolomites), a deposit of Post 



